Tai-Ka·dai (t?-kä?d??) n. A language family including the Tai subfamily and other languages of southern China and Southeast Asia. [Tai + Kadai (coined from ka-, prefix in Laqua (Tai-Kadai language of Vietnam and southern China) k?d?? and Gelao (Tai-Kadai language of Vietnam and southern China) k?tsü, man, human being + Dai).] Tai-Ka?dai? adj. American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.